Behavioural and physiological adaptations of precocial shorebird chicks to Arctic environments

PhD ceremony: Ms. K.L. Krijgsveld, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Behavioural and physiological adaptations of precocial shorebird chicks to Arctic environments

Promotor(s): prof. S. Verhulst, prof. R.E. Ricklefs

Faculty: Mathematics and Natural Sciences

The thesis of Karen Krijgsveld is about the development of precocial chicks of shorebirds in relation to demands set by the arctic environment. In particular, it is about the effects that body size has on growth and development of functional maturity, and on the role of behavioural adaptations in response to environmental and physiological limits to maximize growth.

Being precocial, shorebird chicks leave the nest soon after hatching to forage by themselves, but, as they are not yet homeothermic, they lose body heat while foraging and must be rewarmed by their parents at regular intervals. Because of the active foraging of precocial chicks, a large fraction of their resources is allocated to functions other than growth such as foraging and thermoregulation, compared to more altricial chicks. To deal with the highly varying and often unfavourable environmental conditions, the ability to adjust growth patterns to demand is an important mechanism for increasing chances of survival.

Krijgsveld found that precocial chicks of shorebirds maximize survival by combining a high growth rate with high levels of functional capacity, and are deploying a high flexibility in development and foraging behaviour to adjust to demands set by varying ambient conditions.

Krijgsveld also showed that growth is maximized by maintaining minimum body temperature at relatively high levels of 36-37ºC. In doing so, the chicks maximize the time available for foraging. The physical ability of young precocial chicks to lower their body temperature to values as low as 26ºC is not profitable for growth. The advantage of this phenomenon, which is so typical for shorebird chicks, lies in the fact that it enables them to survive periods of extended cooling, which is extremely useful in the arctic environment.